1. Field of the Invention
The present invention relates to an air purifying agent and a process for producing same. More particularly, the present invention relates to a highly effective air purifying agent which can effectively purify even the environmentally polluted air that has very low concentrations of contaminants and a process for producing same.
2. Description of Prior Art
Nowadays, it has become a large problem to clean the earth's environment. In particular, control and prevention of air pollution is a pressing problem, and there has been a strong demand for purifying polluted air which contains low concentrations of contaminating gaseous substances and is located around all types of environments including working environments in various industries and living environments.
Heretofore, as means for purifying air, dry-type processes and wet-type processes have been known. Among these processes, in view of convenience, a dry-type purification process using activated carbon has been practically utilized. On the other hand, various kinds of air purifying agents which exhibit selective adsorbing effects according to the type of contaminated gas have been developed. For example, an air purifying agent which comprises supporting basic or acidic chemical components on a porous carrier is effective for removal of an acidic gas or basic gas, respectively. Particularly, air purifying agents which comprise supporting an oxidizing or reducing agent on a carrier have been widely used in industrial fields since they have high decomposing and purifying effects on contaminated gases due to their powerful oxidation and reduction abilities.
Such air purifying agents have been proposed in Japanese Patent Application Laid Open Nos. 60-827, 3-23863, etc. These air purifying agents comprise a carrier, such as activated alumina, zeolite, and so on, on which potassium permanganate is supported. Japanese Patent Application Laid Open Nos. 61-68136, 62-161372 and 62-161373 proposed air purifying agents comprising activated carbon on which iodate and/or inorganic acid are supported.
Although these air purifying agents have been made practical in accordance with their intended use, they have some defects in that they not only have certain respective demerits as well as merits, but they are also limited in use since they have peculiar physical properties.
For example, a potassium permanganate-based air purifying agent requires very careful treatment because it is soluble and is a powerful oxidizing agent and, consequently, cannot be used in a conventional domestic field such as in the household environment. On the other hand, although the safety of activated carbon is high when being used, it has disadvantages in that not only is its ratio of removing contaminants in gases limited per se since its main removing mechanism is based on physical adsorption of the contaminants onto the activated carbon, but also in that when the activated carbon is saturated with the contaminants, the adsorbing effect is lost and desorption of the adsorpted contaminants could occur.
Accordingly, in many cases, the choice of a carrier as the air purifying agent as well as the chemical substances to be supported on the carrier is a determining factor on purifying ability and practical application of the air purifying agent.
Furthermore, not only do such prior carriers have relatively high specific gravity since they are mostly comprised of inorganic components, but they also have defects in moldability. Even if they could be molded, they would result in carriers having poor supporting ability and durability. The reason why these phenomena occur is felt to be that the porosity of the carrier is decreased by using a binder or by molding, or that its strength is reduced and deterioration occurs from reaction with contaminants or by the hydroscopic phenomenon.
Recently, in order to improve accuracy or yield of products in the manufacturing field of precision electronics such as semiconductors, or in order to enable permanent preservation of high-class art such as paintings by preventing fading or color changing, there has been a strong demand for the development of an air purifying agent which can completely and safely remove extremely low concentrations of gaseous contaminants in air. On the other hand, there has also been a strong demand for an air purifying agent which is safe to handle and exhibits excellent purifying effects in public use. For such air purifying agents, it is preferable to have as low a weight as possible in view of storage and transport, as well as use.